Some examples: In Maid in Manhattan, rich dude Ralph Fiennes magically lifts J.Lo out of the ghetto, fuelled by sheer love. In Sweet Home Alabama, Reese Witherspoon’s character realizes her true love lies back in the sticks — but only because her old lover has made a name for himself as a designer. Even the “far smarter, better, and otherwise realistic” movie Real Women Have Curves, James notes, falls into this trap: The plucky working-class Latina hero gets into Columbia after a teacher writes a recommendation letter — and the dean admits her, after the normal application deadline has expired, with a full scholarship.

What these movies reveal is not just film’s addiction to fantasy, which audiences expect and embrace, but also to the Big Lie that class is meaningless in American life. Beneath the fairy dust of “Maid in Manhattan” and the grittiness of “Real Women Have Curves” is a similar message: not that America is a classless society, but that class is as fluid as water and upward mobility a cinch.

The idea, of course, goes back to the Founding Fathers’ egalitarian goals, and quickly became so ingrained in the national mythos that what Tocqueville wrote in 1840 could stand as the motto for the J. Lo movie as well as its ancestors like “Sabrina” and “Working Girl”: “At any moment a servant may become a master.” The amalgam of American idealism and rags-to-riches dreams is irresistible.

But that persistent idea ignores the realities of today’s economy and research about social mobility. The aristocratic politician Ralph Fiennes plays in “Maid in Manhattan” precisely fits the profile described by the Princeton economist Alan B. Krueger in a November article in The New York Times, which said that new studies show it takes an average of five or six generations to change a family’s economic position, and that wealth tends to linger in families. Such inherited wealth helps create political dynasties like that of the Bushes and of the Fiennes character — an assemblyman, a senator’s son running for his father’s seat, and not the kind of guy likely to take up with a maid. As Mr. Krueger added in an interview, “Recent trends in income distribution have made upward mobility less likely” than it was even 20 years ago.

And such research isn’t brand new. As Kevin Phillips says in “Wealth and Democracy: A Political History of the American Rich,” published last year, the increasing gap between the median American family income and the richest 1 percent has been “a point of national discussion for over a decade.” By the turn of the 21st century, he writes, the United States “had also become the West’s citadel of inherited wealth.”

Go read the rest of the piece; it gets even better. This issue has annoyed me for years. I keep on leaving movies gnashing my teeth at the loony visions of class transcendance Hollywood sprays at us. I wind up feeling like some grim, Marxist-realist critic from the 1920s.

And ultimately, this underscores the weird irony of Hollywood politics. Theoretically, Hollywood is supposed to be liberal, right? A purveyor of the Red Menace to America, heavily donating to the Democrats, and pushing all manner of environmental causes, right? Sure. But when it comes to actual political philosophy, Hollywood’s writers and producers espouse the sort of naive, bootstrapping Horatio-Algerianism that wouldn’t be out of place at a meeting of the Fed.